A simple variable prism with a linear scale.

PURPOSE: To build a simple, low cost, variable-power prism with a linear scale. METHODS: A sliding lens system, using the prismatic effect of ophthalmic lenses, was constructed. RESULTS: The system functions well at low powers using conventional curved form ophthalmic lenses. CONCLUSIONS: The sliding lens variable prism is a useful alternative to the conventional rotating variable-power prism.

A simple new method for the construction of a ptosis crutch.

A technique by which a ptosis crutch can be fitted in minutes, using readily available and inexpensive materials and tools, is described. No specialist skills are needed and the device can be fitted to existing frames and lenses.